As promulgated by the International Maritime Organization (IMO), issued as Revised MARPOL Annex VI, marine fuels will be capped globally with increasingly more stringent requirements on sulfur content. In addition, individual countries and regions are beginning to restrict sulfur level used in ships in regions known as Emission Control Areas, or ECAs.
Those regulations specify, inter alia, a 1.0 wt % sulfur content on ECA Fuels (effective July 2010) for residual or distillate fuels, a 3.5 wt % sulfur content cap (effective January 2012), which can impact about 15% of the current residual fuel supply, a 0.1 wt % sulfur content on ECA Fuels (effective January 2015), relating mainly to hydrotreated middle distillate fuel, and a 0.5 wt % sulfur content cap (circa 2020-2025), centered mainly on distillate fuel or distillate/residual fuel mixtures. It is noted that this latter 0.5 wt % sulfur content cap corresponds to a global regulation that can potentially affect all non-ECA fuels unless an alternative mitigation method is in place, such as an on-board scrubber. When the ECA sulfur limits and sulfur cap drops, various reactions may take place to supply low sulfur fuels.
The fuels used for larger ships in global shipping are typically marine bunker fuels. Bunker fuels are advantageous since they are less costly than other fuels; however, they are typically composed of cracked and/or resid fuels and hence have higher sulfur levels. Such cracked and/or resid fuels are typically not hydrotreated or only minimally hydrotreated prior to incorporation into the bunker fuel. Instead of attempting to hydrotreat the cracked and/or resid fuels to meet a desired sulfur specification, the lower sulfur specifications for marine vessels can be conventionally accomplished by blending the cracked and/or resid fuels with distillates. While blending with distillate fuels can be effective for reducing sulfur levels, such low sulfur distillate fuels typically trade at a high cost premium for a variety of reasons, not the least of which is the utility in a variety of transport applications employing compression ignition engines. Conventionally, distillate fuels are produced at low sulfur levels, typically significantly below the sulfur levels specified in the IMO regulations.
It would be advantageous to develop alternative sources of blendstock for blending with cracked and/or resid fuels to provide lower cost alternatives when forming marine fuel oils with a sulfur content of 0.5 wt % or less. Additionally or alternately, it would be advantageous to develop alternative sources of blendstock to provide lower cost alternatives when forming marine gas oils.